Serial data transmission is employed in a wide variety of computer-communication applications such as in the industry standard RS-232 communications interface and in modem telecommunications. Various serial data transmission encoding systems have been devised. In a typical system the binary data in the form of logic "1" and logic "0" signals are encoded on the transmission medium by the presence or absence of a voltage or a pulse. These logic signals are transmitted in streams and include clock or synchronizing signals for use by the data receiver in controlling the various logic operations required to extract the encoded binary data from the stream.
In other encoding systems, the binary data, rather than being transmitted in the form of the presence or absence of a pulse, is represented by the relative widths of the data pulses. Such a system is disclosed in U.S. Pat. No. 4,066,841 to Young. In Young, the binary data are encoded into a serial biphase data stream and the time intervals between phase transitions in the biphase stream are used to represent logic "1" and logic "0" states of the encoded binary data. Thus, the system of Young allows for relatively high bandwidth because successive encoded binary data in the stream do not need to be separated by a non-code carrying time segment.